I received a broken Philips 42PF7220A37 Plasma TV where the display is distorted as a gift. When I first plugged it in the screen had a black horizontal bar at the top and a bunch of distortions. I opened the TV up and disconnected all the ribbon cables on the 2 buffer boards and then plugged them back in (to make sure nothing was loose). When I did this the horizontal bar went away but I still get a series of distortions.
I purchased a service guide for this TV with block diagrams, schematics, and more. I'd be willing to share this with someone that is willing to help.
I do not want to blindly start replacing parts. I am hoping I can do some actual troubleshooting to determine what needs to be replaced. I am an experianced electronics test tech and have access to meters, scopes, logic anylizers, and other test equipment. So I am comfortable probing various components.
Here is the picture when I first got the TV:
http://img411.imageshack.us/img411/4041/dscf6064h.jpg
Here it is after I reseated the ribbon cables:
http://img96.imageshack.us/img96/7206/dscf6066.jpg
I don't know if the change was actually due to reseating the cables or just a coincidence. Originally I was told this TV was producing no picture so maybe it goes through random phases. The last picture has been that way since I did that 2 days ago.
Help would be appreciated. Thank you.

It is either the sustain board or one of the buffer boards. Since you have the service manual you should have no problem testing these. Start by checking the capacitors if they read an overload or a value that is below the specified value. Problems like these are caused by voltage drops especially on the sustain boards. There should be two of them X-sus and Y-sus. Ypu should start by testing both of them to zero in on the source of the problem.

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Download philips latest firmware here: Click sometimes glitches can be cleared with their firmware. Also this could be a sign that your vertical buffer drivers are over-heating due to a faulty Y-sustain problem. The best way to check is to remove the back cover turn the TV on and see which buffer IC is getting red hot by touching it. Be careful as the voltage levels are dangerous, get someone who's technically proficient to do that little test for you....
http://tvtechwork.webs.com/

if it is limited to external glass the glass can be ordered separately but if there is internal crack on pdp itself would have to replace pdp. from my experience generally if it limited to crack on external glass there still should be picture so there may be additional damage to plasma display itself

Un plug the power to the Plasma Screen and also to the Media Receiver for ten minutes. Disconnect the off the air antennas both A and B. After ten minutes plug in the plasma screen then the media receiver and turn on wi the remote control. You should now be back in operation. I was.
Also It may not be a bad digital tuner. The TV Guide feature is active even when the zip code is set to all 0s so if you have an over the air antenna attached the TV will look for the TV Guide info and if it can not find it because of a weak signal or the chanel it is tuned to does not carry that information the TV thinks that tuner does not work which triggers the 12 flashes. Also on power up the gray box with the waring message "Plasma Display Starting Up, Please Wait" appears and the screen is blank.

Un plug the power to the Plasma Screen and also to the Media Receiver for ten minutes. Disconnect the off the air antennas both A and B. After ten minutes plug in the plasma screen then the media receiver and turn on wi the remote control. You should now be back in operation. I was.
Also It may not be a bad digital tuner. The TV Guide feature is active even when the zip code is set to all 0s so if you have an over the air antenna attached the TV will look for the TV Guide info and if it can not find it because of a weak signal or the chanel it is tuned to does not carry that information the TV thinks that tuner does not work which triggers the 12 flashes. Also on power up the gray box with the waring message "Plasma Display Starting Up, Please Wait" appears and the screen is blank.

You can go into the menu and adjust the picture setting. If that does not fix the iss and the set is under a year old then it will still be in warranty. Contact Philips at 1-88- 744-5477 and have them do the repairs under warranty. Don't do it your self because that will void your warranty.